Illumination of samples of various types is commonly practiced for many applications in medicine, biology, chemistry and other fields. Absorbance and fluorescence measurements are used in numerous applications. Dedicated instruments such as fluorescence microscopes tend to be bulky and expensive for portable applications as well as confocal optics due to various lenses, filters and opto-mechanical structures involved. The cost is high due to lenses, optical sources and various other elements involved in building a complete system.
In fluorescence related measurements, the problem of stray light can be significant. It can adversely affect the signal to noise ratio (SNR) and detection sensitivity. Typically, optical filters and dichroic mirrors are used which can be expensive. As the size of sample increases, the beam diameter increases, requiring larger optical elements and further increasing costs. Even a small sample of a few microliters can take up significant area if filled in a reservoir of small height.